title: A preliminary fMRI study of analgesic treatment in chronic back pain and knee osteoarthritis.
abstract: The effects of an analgesic treatment (lidocaine patches) on brain activity in chronic low back pain (CBP) and in knee osteoarthritis (OA) were investigated using serial fMRI (contrasting fMRI between before and after two weeks of treatment). Prior to treatment brain activity was distinct between the two groups: CBP spontaneous pain was associated mainly with activity in medial prefrontal cortex, while OA painful mechanical knee stimulation was associated with bilateral activity in the thalamus, secondary somatosensory, insular, and cingulate cortices, and unilateral activity in the putamen and amygdala. After 5% lidocaine patches were applied to the painful body part for two weeks, CBP patients exhibited a significant decrease in clinical pain measures, while in OA clinical questionnaire based outcomes showed no treatment effect but stimulus evoked pain showed a borderline decrease. The lidocaine treatment resulted in significantly decreased brain activity in both patient groups with distinct brain regions responding in each group, and sub-regions within these areas were correlated with pain ratings specifically for each group (medial prefrontal cortex in CBP and thalamus in OA). We conclude that the two chronic pain conditions involve distinct brain regions, with OA pain engaging many brain regions commonly observed in acute pain. Moreover, lidocaine patch treatment modulates distinct brain circuitry in each condition, yet in OA we observe divergent results with fMRI and with questionnaire based instruments.
authors.affiliation: Department of Physiology, Northwestern University, Feinberg School of Medicine, 303 East Chicago Ave, Chicago IL 60611, USA. m-baliki@northwestern.edu
authors.forename: Marwan N
authors.initials: MN
authors.lastname: Baliki
authors.forename: Paul Y
authors.initials: PY
authors.lastname: Geha
authors.forename: Rami
authors.initials: R
authors.lastname: Jabakhanji
authors.forename: Norm
authors.initials: N
authors.lastname: Harden
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Schnitzer
authors.forename: A Vania
authors.initials: AV
authors.lastname: Apkarian
mesh_terms: D000328:Adult; D000368:Aged; D000698:Analgesia / Q000379:methods*; D001416:Back Pain / Q000188:drug therapy / Q000503:physiopathology*; D001931:Brain Mapping; D002908:Chronic Disease; D005260:Female; D006179:Gyrus Cinguli / Q000187:drug effects / Q000503:physiopathology; D006801:Humans; D008012:Lidocaine / Q000008:administration & dosage / Q000494:pharmacology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000188:drug therapy / Q000503:physiopathology*; D017397:Prefrontal Cortex / Q000187:drug effects / Q000503:physiopathology; D011795:Surveys and Questionnaires; D013788:Thalamus / Q000187:drug effects / Q000503:physiopathology
chemical_list: D008012:Lidocaine